With the development of wireless multimedia services, demands of people for high data rate and user experience are increasing, so as to make higher requirements for system capacity and coverage of a traditional cellular network. In addition, application scenarios of public security, social networking, near field data sharing, local advertising and the like enable demands of people, for knowing people or things nearby and communicating therewith (proximity services), to gradually increase. A traditional base station-centered cellular network has obvious limitations to high data rate and supporting of the proximity services, and under this demand background, a Device-to-Device (D2D) (i.e., device direct-through) technology representative of a new development direction of future communication technologies emerges. Application of the D2D technology can alleviate burdens on the cellular network, reduce the power consumption of a battery of a User Equipment (UE), increase the data rate, improve the robustness of network infrastructure, and well meet requirements for the above-mentioned high data rate services and proximity services.
The D2D technology can work at a licensed band or an unlicensed band to allow a plurality of D2D UEs supporting a D2D function to perform direct discovery/direct communication in the presence of network infrastructure or in the absence of network infrastructure. There are mainly three D2D application scenarios as follows.
UE1 and UE2 perform data interaction under the coverage of a cellular network, and user plane data does not pass through network infrastructure, as shown in Mode 1 in FIG. 1.
A UE in a weakly covering/coverless area performs relayed transmission, as shown in Mode 2 in FIG. 1. UE4 with poor signal quality is allowed to communicate with a network via proximal UE3 covered by the network, and coverage expansion and capacity improvement of an operator can be assisted.
When an earthquake or an emergency occurs and a cellular network cannot normally work, inter-device direct communication is allowed, as shown in Mode 3 in FIG. 1. Control planes and user planes among UE5, UE6 and UE7 perform one-hop or multi-hop data communication without passing through network infrastructure.
The D2D technology usually includes a D2D discovery technology and a D2D communication technology, herein the D2D discovery technology refers to a technology for judging/determining whether a first UE is proximal to a second UE. Usually, D2D UEs may discover each other by transmitting or receiving discovery signals/information. The D2D communication technology refers to a technology of direct communication in a manner that some or all items of communication data between the D2D UEs may not pass through network infrastructure.
On the basis of the above features and advantages of the D2D technology, the related art has been possible to use cellular wireless communication and D2D technologies so as to achieve vehicle networking applications, and main scenarios supporting communications include instant communication and vehicle warning.
As for the vehicle warning, an investigation report from the US National Highway Traffic Safety Administration shows that 80% of highway traffic accidents are caused by negligence of drivers within 3 s before the accidents occur. An experiment of Daimler-Benz shows that if drivers are warned ahead of 0.5 s, 60% of rear-end collisions can be avoided; and if drivers can be warned ahead of 1.5 s and take measures, 90% of rear-end collisions can be avoided. A communication-based collision warning system achieves real-time information interaction between vehicles and between a vehicle and roadside infrastructure by using an advanced wireless cellular communication technology, informs each other of a current state (including position, speed, acceleration and driving path of vehicle) and obtained road environment information, cooperatively senses a road danger situation, provides multiple pieces of collision warning information in time, prevents occurrence of highway traffic safety accidents, and becomes a new idea of attempting to solve the problem of highway traffic safety for each country at present.
The vehicle warning may probably include collision warning, lane change warning and the like. However, delays are highly required under this scenario, and the related D2D technology cannot be achieved.
For some other items of service data needing to be transmitted with low delays, a special resource allocation mechanism for transmitting service data is not designed in the related art. According to the related resource allocation manner, delays for transmitting low-delay data cannot meet real-time demands.